This section provides background information related to the present disclosure which is not necessarily prior art.
High-energy density, electrochemical cells, such as lithium ion batteries and lithium sulfur batteries can be used in a variety of consumer products and vehicles, such as Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs). Typical lithium ion and lithium sulfur batteries comprise a first electrode (e.g., a cathode), a second electrode (e.g., an anode), an electrolyte material, and a separator. Often a stack of battery cells are electrically connected to increase overall output. Conventional lithium ion and lithium sulfur batteries operate by reversibly passing lithium ions between the negative electrode and the positive electrode. A separator and an electrolyte are disposed between the negative and positive electrodes. The electrolyte is suitable for conducting lithium ions and may be in solid or liquid form. Lithium ions move from a cathode (positive electrode) to an anode (negative electrode) during charging of the battery, and in the opposite direction when discharging the battery.
Battery separators can be made by wet or dry processes to have an adequate porosity. The pores hold the electrolyte material, which enables ions to move between the first electrode and the second electrode. The process used to create pores in conventional lithium ion battery separators requires precise stretching of an extruded thin film. However, when these separators are exposed to heat, they endure shrinkage that increases the risk of battery shorting. It would be desirable to develop methods of producing porous battery separators that possess good thermal stability at a high production rate.